Method and apparatus to improve the properties of ion beam deposited films in an ion beam sputtering system

ABSTRACT

An ion beam sputtering system having a chamber, an ion beam source, a multiple targets, a shutter, and a substrate stage for securely holding a wafer substrate during the ion beam sputtered deposition process in the chamber. The substrate stage is made to tilt about its vertical axis such that the flux from the targets hit the wafer substrate at a non-normal angle resulting in improved physical, electrical and magnetic properties as well as the thickness uniformity of the thin films deposited on the substrate in the ion beam sputtering system.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to the fabrication of thin films by ionbeam sputter deposition and, more particularly, to the fabrication ofmultilayered thin film structures such as magnetoresistive sensors byion beam sputter deposition wherein the properties of multiple layersdeposited on a substrate are controlled by controlling the angle atwhich atoms are deposited on the substrate.

2. Description of Related Art

It is well-known in the art to utilize radio frequency (RF) or directcurrent (DC) magnetron sputter-deposition system for fabrication of thinfilm devices such as magnetic recording sensors (e.g., magnetoresistivesensors) and storage media. Such sputter-deposition systems arecharacterized by crossed electric and magnetic fields in an evacuatedchamber into which an inert, ionizable gas, such as argon, isintroduced. The gas is ionized by electrons accelerated by the electricfield, which forms a plasma in proximity to a target structure. Thecrossed electric and magnetic fields confine the electrons in a zonebetween the target and substrate structures. The gas ions strike thetarget structure, causing ejection of atoms that are incident on aworkpiece, typically a wafer substrate on which it is desired to depositone or more layers of selected target materials.

In the conventional sputtering deposition systems relatively highoperating pressures are utilized in order to obtain films having lowinternal stress which results in non-directional sputtering flux at thesubstrate. However, this non-directional flux introduces manufacturingprocess difficulties as device dimensions become increasingly smaller.

It is known to utilize ion beam sputter deposition in certainapplications to overcome some of the difficulties encountered withconventional RF/DC sputter techniques. Several aspects of ion beamsputter deposition systems differ from conventional sputter depositionsystems and provide significant advantages. For example, (1) the use oflow background pressure results in less scattering of sputteredparticles during the transit from the target to the wafer substrate; (2)control of the ion beam directionality provides a variable angle ofincidence of the beam at the target; (3) a nearly monoenergetic beamhaving a narrow energy distribution provides control of the sputteryield and deposition process as a function of ion energy and enablesaccurate beam focusing and scanning; and (4) the ion beam is independentof target and substrate processes which allows changes in target andsubstrate materials and geometry while maintaining constant beamcharacteristics and allowing independent control of the beam energy andcurrent density.

Apparatus and methods for depositing a thin layer of material on asubstrate utilizing ion beam sputtering deposition systems aredescribed, for example, in U.S. Pat. No. 4,923,585 ('585) to Krauss etal. and in U.S. Pat. No. 5,942,605 to Pinarbasi ('605), the contents ofwhich are incorporated herein by reference. The '585 patent disclosesthe use of a computer controlled, single ion beam with a quartz crystalmonitor to produce deposited films of arbitrary composition as well aslayered structures of arbitrary thickness from multiple targets ofdifferent materials. The '605 patent discloses matching the ion beam gasatomic mass to the target material atomic mass to produce thin filmshaving densities and physical properties very close to their bulkproperty values. While the '585 and '605 patents disclose methods fordepositing multilayer films, the problems of controlling the amount offlux deposited at the junction between the layers deposited adjacent toeach other is not addressed.

Ion beam sputter deposition systems have been utilized to depositindividual layers of anisotropic magnetoresistive (AMR) sensors andgiant magnetoresistive (GMR) sensors for use in magnetic disk drives. Inthe GMR sensors, for example, the resistance of the magnetoresistive(MR) sensing layer varies as a function of the spin-dependenttransmission of the conduction electrons between the ferromagneticlayers separated by a non-magnetic layer (spacer) and the accompanyingspin-dependent scattering which takes place at the interface of theferromagnetic and non-magnetic layers and within the ferromagneticlayers. GMR sensors using only two layers of ferromagnetic material(e.g., NiFe or Co or NiFe/Co) separated by a layer of GMR promotingnon-magnetic metallic material (e.g., copper) are generally referred toas spin valve (SV) sensors. U.S. Pat. No. 5,206,590 to Dieny et al.('590), the content of which is incorporated herein by reference,discloses an MR sensor operating on the principle of GMR.

Magnetoresistive (MR) sensors (AMR or GMR) are very small devices thatare generally fabricated by sputtering depositions on large wafersubstrates which are generally larger than 5 inches in diameter to formthousands of sensors. The wafer is subsequently diced to form individualmagnetic read transducers for use in magnetic storage devices.

One of the major issues in the fabrication process of MR sensors is toprecisely control the physical, electrical and magnetic properties ofthe junction formed between the layers deposited adjacent to each other.An example of such a junction is the contiguous junction formed betweenthe MR layer and the longitudinal biasing layer in an MR sensor.

Another critical issue in the fabrication process of MR sensors is thethickness uniformity of each and every deposited layer over the entireutilized area of a given wafer in order to control the uniformity ofoperating characteristics (for example, resistance andmagnetoresistance) of the entire batch of the MR sensors fabricated onsaid given wafer.

In an experiment by the present applicant, an ion beam sputtering system120 (FIG. 1) was developed and used to determine the properties of thejunction formed between the layers deposited adjacent to each other andthickness uniformity of various layers deposited in the end region 206and 204 of the SV sensor 200 (FIG. 2A) formed on a 5 inch diameter wafersubstrate (FIG. 3).

Referring to FIG. 1, there is shown a simplified diagram illustratingthe ion beam sputter deposition system 120 developed and used by theApplicant. The ion beam sputter deposition system 120 includes a vacuumchamber 122 in which an ion beam source 121 is mounted. The ion beamsystem 120 further comprises selectable multiple targets 123, formed ormounted, on a rotary target support 125. An ion beam 133 provided by theion beam source 121 is directed at one of the targets on the selectablemultiple targets 123 where the impacting ions cause sputtering of theselected target material. The sputtered atoms 126 emitted from theselected target material is directed at a near-normal angle (85 to 95degrees) onto a workpiece (wafer substrate, wafer, deposition substrate)131 on which is formed a layer of the selected target material. Thesputtered atoms 126 hit (bombard) the workpiece 131 at a near-normalangle (85 to 95 degrees). The workpiece 131 is placed securely, viaclamps or vacuum suction (not shown) on a substrate stage (workpiecestage) 141. The substrate stage 141 is retrievable into a loading port139 via a gate valve 138 for changing the workpiece 131.

A thickness monitor 137, positioned closely adjacent to the workpiece131, provides real-time, in-situ monitoring of the thickness of thegrowing film during deposition over the entire utilized area of theworkpiece 131. A non-movable flux regulator 150 fixed in front of theworkpiece 131 partially blocks the sputtered atom flux and is used inconjunction with rotation of the workpiece 131 to improve thicknessuniformity of the deposited layer during the deposition process. Thenon-movable flux regulator refers to a flux regulator that its positionis fixed prior to the ion beam sputtering deposition of one or moredeposited layers and remains fixed during the whole deposition process(i.e., the position of the flux regulator is never changed during thedeposition process of said one or more deposited layers). Duringoperation of the ion beam sputter deposition system, the vacuum chamber122 is maintained at suitable low pressure by a vacuum pump (not shown)via port 135.

Now referring to FIG. 2A, there is shown a cross section of the SVsensor 200 having end regions 204 and 206 separated from each other by acentral region 202 where Applicant's ion beam sputtering system 120 wasused to deposit seed, biasing and lead layers in said end regions. Afree layer (free MR layer, free ferromagnetic layer) 210 is separatedfrom a pinned layer (pinned MR layer, pinned ferromagnetic layer) 220 bya non-magnetic, electrically-conducting spacer layer 215. Alternatively,pinned layer 220 may be made of multi layers of ferromagnetic material(e.g., cobalt, Nife) separated from each other by a metallicnon-magnetic conductor (e.g., ruthenium). Such a multi-layer pinnedlayer is generally referred to as anti-parallel (AP) pinned layer. Themagnetization of the pinned layer 220 is generally, although notnecessarily, is fixed (i.e., pinned) through exchange coupling with anantiferromagnetic (AFM) layer 225. The AFM layer 225, is generally madeof NiMn, FeMn or NiO. The magnetization of the free layer, however, isfree to rotate in response to an external field. Free layer 210, spacerlayer 215, pinned layer 220 and the AFM layer 225 (if used), which arecollectively referred to as MR material, are all formed in the centralregion 202 over the substrate 228. Hard bias (HB) layers 230 and 235which are formed in the end regions 204 and 206, respectively, providelongitudinal bias for the MR free layer 210. Hard bias layers 230 and235 are generally, although not necessarily, deposited over seed layers280 and 285, respectively. Hard bias layers 230 and 235 form contiguousjunctions 274 and 276, respectively, with at least the free layer 210.Leads 240 and 245 which are formed over the hard bias layers 230 and235, respectively, provide electrical connections for the flow of thesensing current I_(s) from the current source 260 to the MR sensor 200.The MR material further has first and second side edges 270 and 272(FIG. 2B).

FIG. 3 shows a wafer 300 manufactured by Applicant's ion beam sputteringsystem for making SV sensors. FIG. 3 illustrates schematically thegeneral pattern of several blocks 301, each block comprising a pluralityof rows 302. Each of the rows 302 comprises a plurality of SV sensors(such as SV sensor 200 or 900) disposed along each row and formed on thewafer substrate 306.

As mentioned earlier, Applicant conducted an experiment in which the ionbeam sputtering system 120 was used to build SV sensors 200 on the wafersubstrate 306. In doing so, layers of sputtered material comprising thelayer structure of the central region 202 of the SV sensor 200 wereindividually deposited on the whole wafer. Photoresist materials 290 and291 were then deposited on the whole wafer, after which they wereexposed to light in selected regions and developed to provide openingsfor removal of the deposited materials outside of the central region202. FIG. 2B shows the step in the manufacturing process of the SVsensor 200 after photoresists 290 and 291 have been developed and thedeposited materials outside of the central region 202 have been removedusing ion-milling. Following the step shown in FIG. 2B, seed layermaterial, hard bias material and lead materials were sputtered depositedsequentially in the end regions 204 and 206. The materials deposited inthe end regions 204 and 206 were sputtered deposited at near-normal (85to 95 degree) angle as shown by arrows 292 (FIG. 2C).

Close examination of the SV sensor 200 (FIG. 2A) reveals the followingshortcomings present in the SV sensor 200 formed according to theaforementioned steps:

(i) the thickness of the seed layers 280 and 285 are not uniform;

(ii) the thickness of the hard bias layers 230 and 235 are not uniform;hard bias layers 230 and 235 taper off by the first and second sideedges 270 and 272, respectively; and a notch is formed in each of thehard bias layers 230 and 235 adjacent to the MR material side edges 270and 272. Hard bias tapering results in low coercivity hard bias materialdeposited at the edges of the MR material resulting in MR sensorinstability during the read operation; and

(iii) the thickness of the lead layers 240 and 245 are not uniform andthey taper off near the MR material side edges 270 and 272. Leadtapering results in loss of electrical signal.

Furthermore, Applicant conducted another experiment in which the ionbeam sputtering system 120 was used to build SV sensors 200 on theutilized area of the wafer substrate 306 and the uniformity of thedeposited layers across the entire utilized area of the wafer weremeasured by measuring the sheet resistance of each deposited layer atthe five positions 305 indicated on a diameter of the wafer 300. Theuniformity of the sheet resistance across the wafer is expressed as apercent uniformity which is a measure of the maximum variation in thefilm thickness that may be seen on a given wafer.

FIG. 4 is a graph showing the normalized sheet resistance of the Cuspacer film 215 of the SV sensor 200 measured at five positions 305across the wafer 300. As shown in FIG. 4, the Cu film thickness variedby as much as 11.3% across the utilized area of the wafer 300. The NiFeand Co layer thicknesses, measured at the same five locations 305 acrossthe wafer 300, varied by about 3.5% and 2.7%, respectively.

Eleven and Three Tenth percent (11.3%) variation in the thickness of theCu spacer film across the wafer 300 means that many of the MR sensors onwafer 300 fail to work properly or have unacceptably large variations intheir responses. Also, as the size of the wafer increases to improveproductivity, the problem of achieving film uniformity across the waferbecomes even worse.

The prior art does not address or acknowledge the problems associatedwith:

(i) lack of seed layer, hard biasing layer and lead layer thicknessuniformities in each MR sensor built in an ion beam sputter depositionsystem;

(ii) poor physical, electrical and magnetic properties at the contiguousjunction between materials deposited adjacent to each other; and

(iii) lack of thickness uniformity of thin layers deposited over theentire utilized area of the wafer in an ion beam deposition system.

Therefore, there is a need for an invention of a method and apparatusfor controlling the properties and thickness of individual films of amultilayer thin film structure deposited adjacent to each other on awafer substrate in an ion beam sputtering system.

There is a further need for an invention of a method and apparatus forcontrolling the thickness uniformity of individual films of a multilayerthin film structure deposited on a wafer substrate in an ion beamsputtering system.

There is also a further need for an invention disclosing a method andapparatus to control the thickness of individual layers of themultilayer structures of MR sensors deposited adjacent to each other ona wafer substrate in an ion beam sputtering system.

SUMMARY OF THE INVENTION

It is an object of the present invention to disclose an ion beamsputtering system having a substrate stage that can be made to tiltthrough a predefined angle.

It is a further object of the present invention to disclose an ion beamsputtering system having a substrate stage that can be made to tilt andform a non-normal angle with respect to its vertical axis, before orduring the deposition process.

It is yet another object of the present invention to disclose an ionbeam sputtering system having a substrate stage connected to a stage armwhere the substrate stage can be made to tilt about the major axis(longitudinal axis) of the stage arm.

It is still another object of the present invention to disclose an ionbeam sputtering system having a substrate stage connected to a stage armwhere the substrate stage can tilt about the minor axis of the stagearm.

It is another object of the present invention to disclose an ion beamsputtering system having a substrate stage that can rotate while it istilted.

It is a further object of the present invention to disclose an ion beamsputtering deposition process for building MR (AMR, GMR or SV) sensorswith improved physical properties of each of the individual layers ofthe multilayer structures deposited on a wafer substrate.

It is yet another object of the present invention to disclose an ionbeam sputtering system having a tiltable substrate stage and a movableflux regulator.

These and other objects of the present invention are accomplished byApplicant's invention of an ion beam sputter deposition system where aworkpiece is securely placed on the top surface of the substrate stageduring the ion beam sputtering deposition process. The substrate stagecan be made to tilt and form a non-normal angle with respect to itsvertical axis such that the workpiece also forms a non-normal angle withrespect to the incoming deposition atoms. The substrate stage is furthermade to rotate about its vertical axis while it is also tilted withrespect to its vertical axis. The tilting substrate stage allowscontrolling the physical properties of the films deposited by allowingthe sputtered atoms (flux) to be deposited on the workpiece at anon-normal deposition angle (i.e., an angle which is different from 90degree).

The ion beam sputter deposition system further includes a flux regulatorlocated between the target and the workpiece which can be made to move,relative to the substrate, in each of the three orthogonal X, Y and ZCartesian directions as well as rotation about its longitudinal axis andswinging in a plane of a predefined axis through a predefined angle. Theposition of the movable flux regulator relative to the workpiece affectsthe thickness uniformity of thin films deposited on and across theentire utilized area of the wafer. The best position of the movable fluxregulator has been found, through experimentations, to be different fordifferent materials deposited from different targets in the same ionbeam system. Applicant's movable flux regulator refers to a fluxregulator that its position, relative the workpiece, can be changeddepending on the material being deposited.

Therefore, Applicant's ion beam sputtering system having a tiltablesubstrate stage allows sputtered flux deposition on the workpiece at anon-normal angle thus substantially improving the physical, electricaland magnetic properties of the contiguous junctions formed between thelayers deposited adjacent to each other. Furthermore, Applicant's ionbeam sputtering system having a movable flux regulator provides meansfor achieving uniform thickness for each layer deposited over the entireutilized area of a wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and advantages of the presentinvention, as well as the preferred mode of use, reference should bemade to the following detailed description read in conjunction with theaccompanying drawings.

FIG. 1 is a block diagram of an ion beam sputtering deposition system;

FIG. 2A is an air-bearing surface view, not to scale, of a SV sensorconnected to a current source;

FIG. 2B is an air-bearing surface illustration, not to scale, of a stepin making the SV sensor of FIG. 2A;

FIG. 2C is an air-bearing surface illustration, not to scale, of anotherstep in making the SV sensor of FIG. 2A;

FIG. 3 is a plan view of a wafer showing the general pattern of SVsensors formed on the wafer in Applicant's ion beam sputter depositionsystems;

FIG. 4 is a graph showing the variation in sheet resistance of a copperlayer across the wafer of FIG. 3 deposited using the ion beam sputteringsystem of FIG. 1;

FIG. 5 is a block diagram of the preferred embodiment of the ion beamsputtering system of the present invention having a tilting substratestage;

FIG. 6A is a drawing, not to scale, showing the substrate stage of thepresent invention in relation to the movable flux regulator positionedbetween the target and substrate in the ion beam sputtering system ofthe present invention;

FIG. 6B is an alternative embodiment of the invention shown in FIG. 6A;

FIGS. 7A and 7B are drawings, not to scale, showing the tiltablesubstrate stage of the present invention tilting about its vertical axisdownward and upward, respectively;

FIGS. 8A and 8A' are frontal and side (as seen in plane 5--5) views,respectively, of the substrate stage of the present invention withouttilting;

FIGS. 8B and 8B' are frontal and side views, respectively, of thesubstrate stage of the present invention tilting about its longitudinalaxis in a first direction;

FIGS. 8C and 8C' are frontal and side views, respectively, of thesubstrate stage of the present invention tilting about its longitudinalaxis in a second direction;

FIG. 9A is an ABS illustration, not to scale, of the photoresistdeposition step in manufacturing the MR sensor 900 in the ion beamsputtering system of the present invention having a tiltable substratestage;

FIG. 9B is an ABS illustration, not to scale, of the photoresistdevelopment step in manufacturing the MR sensor 900 in the ion beamsputtering system of the present invention;

FIG. 9C is an ABS illustration, not to scale, of the seed materialdeposition step in manufacturing the MR sensor 900 in the ion beamsputtering system of the present invention;

FIG. 9D is an ABS illustration, not to scale, of the hard biasedmaterial deposition step in manufacturing the MR sensor 900 in the ionbeam sputtering system of the present invention;

FIG. 9E is an ABS illustration, not to scale, of the lead materialdeposition step in manufacturing the MR sensor 900 in the ion beamsputtering system of the present invention;

FIG. 9F is an ABS view of the MR sensor 900 manufactured using the ionbeam sputtering system of the present invention having a tiltablesubstrate stage;

FIG. 10 is a drawing, not to scale, showing a block diagram of analternative embodiment of the present invention having a tiltablesubstrate stage;

FIG. 11 is a graph showing the copper sheet resistance uniformity acrossthe deposition substrate as a function of X-setting of the movable fluxregulator of the present invention; and

FIG. 12 is a graph showing the cobalt sheet resistance uniformity acrossthe deposition substrate as a function of X-setting of the movable fluxregulator of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following description is the best embodiment presently contemplatedfor carrying out the present invention. This description is made for thepurpose of illustrating the general principles of the present inventionand is not meant to limit the inventive concepts claimed herein.

Referring now to FIGS. 5 through 8, there are shown several diagrams ofthe ion beam sputtering deposition system (ion beam system, IBS) 500 ofthe present invention. The ion beam system 500 comprises a vacuumchamber 522 exhausted to a suitable low pressure by a vacuum pump 507via port 505 which can be closed by a gate valve 506. An ion beam source521 directs energetic ions 533 at a selectable multiple targets 523 ofone or more materials where the impacting ions cause sputtering of theselected target material. The sputtered atoms 526 emitted from theselected target material are then sputter deposited on a workpiece(wafer) 531. Workpiece 531 is a wafer similar to the wafer 300 shown inFIG. 3. The ion beam source 521 may be any suitable ion beam source suchas a Kaufman source. The selectable multiple targets 523 is generallymounted on a rotary target support 525. Alternatively, a single targetof material may be used instead of the selectable multiple targets 523.

The ion beam system 500 further includes a substrate stage 541 having atop surface 532, a longitudinal axis 537 lying in the plane of the topsurface 532 and a vertical axis 535 which is perpendicular to the topsurface 532. The substrate stage 541 is connected to a stage arm 543 viamechanical gears (not shown). The stage arm 543 which has a longitudinalaxis 564 and a vertical axis 566, is in turn connected to a stagecontroller 560 via a connection point 568 which generally includesmechanical gears for controlling the stage arm 543 motions. Stagecontroller 560 is in turn connected and controlled by a control system570. Workpiece 531 is securely mounted, via clamps (not shown) orthrough vacuum suction (not shown), on the substrate stage 541 such thatthe tilting and/or rotation of the substrate stage 541 causes thetilting and/or rotation of the workpiece 531. In the preferredembodiment of the present invention, substrate stage 541 can be made totilt by rotating the stage arm 543 about its longitudinal (major) axis564. As a result, substrate stage 541 tilts with respect to the verticalaxis 535 such that the top surface 532 forms a non-normal angle withrespect to the vertical axis 535. Consequently, top surface of theworkpiece 531 forms a non-normal angle with respect to the sputteredatoms 526 emitted from the selected target material. In the preferredembodiment of the present invention, substrate stage 541, is preferablya circular stage which can also be made to rotate about the verticalaxis 535, using a rotary/linear motor (not shown), during any depositionstep in order to rotate the workpiece 531.

Communication buses 561, 563, 565 and 567, connecting the control system570 to the stage controller 560, are utilized to transfer informationbetween the control system 570 and the stage controller 560 such aswhether substrate stage 541 should rotate or not, how fast it shouldrotate, whether substrate stage 541 should tilt, and in which directionit should tilt. Once the control system 570 issues commands to the stagecontroller 560 such as commands for rotating, rotation speed, tiltingand/or moving upward or downward the substrate stage 541 and tiltingdirection during a film deposition process, stage controller 560 in turncontrols the substrate stage 541 rotation, rotation speed, tilting andtilting direction via the stage arm 543. The stage arm 543 is connectedto the stage controller 560 via the connection point 568 such that thestage arm 543 can be made to tilt, rotate and pivot in all directions(X-direction, Y-direction, Z-direction, XY-plane, XZ-plane, andYZ-plane) about the connection point 568. In the preferred embodiment ofthe present invention, substrate stage 541 is made to tilt by rotatingthe stage arm 543 about its longitudinal axis 564 (FIGS. 8A-8A', 8B-8B',and 8C-8C'). Alternatively, the substrate stage 541 may be made to tiltby moving the stage arm 543 up or down about the connection point 568(FIGS. 7A-7B) such that the stage arm 543 forms a non-normal angle withthe vertical axis 566.

The ion beam system 500 further comprises a movable flux regulator 550connected to a flux regulator shaft 551. Flux regulator shaft 551 has afirst end 552 and a second end 554. In the preferred embodiment of thepresent invention, flux regulator shaft 551 movement is made totallyindependent of the stage arm 543 movement by connecting the second end554 of the shaft 551 directly to a flux regulator controller 540 (FIGS.5 and 6B) mounted on the wall of the chamber 522. Alternatively, thesecond end 554 of the flux regulator shaft 551 may be connected to aflux regulator arm 553 where the flux regulator arm 553 is in turnconnected to the stage arm 543 as shown in FIG. 6A. Flux regulator 550is positioned between the target 523 and the workpiece 531 so as topartially block the sputtered atom flux 526 from colliding with theworkpiece 531 and thus modifying the flux distribution deposited on thewhole workpiece 531. Flux regulator 550 proper operation depends on thecontinuous rotation of the workpiece 531 about the vertical axis 535,during each deposition step, in order to average the incident sputteredatom flux. Because the incident sputtered atom flux is generally highestat the center of the substrate, the preferred shape of the movable fluxregulator 550 is an arrowhead-like shape whose width increases graduallyfrom the tip 556 to a maximum width 557 (about 2.5 cm) and thengradually decreases (tapering off) to the width of the flux regulatorshaft 551. The length of the flux regulator 550 from its tip 556 to thefirst end 552 of the flux regulator shaft 551 is about 5 cm.Arrowhead-shape of the flux regulator 550 results in greater blockage ofthe atom flux at the inner radii of the workpiece 531 than at the outerradii. The flux regulator 550 is movable relative to the workpiece 531by moving the flux regulator shaft 551 which can move about theconnection point 555 (FIGS. 6A-6B). In the case of the embodiment shownin FIG. 6A, the flux regulator 550 may also be made to move by movingthe flux regulator arm 553. The flux regulator controller 540 isgenerally fitted with three orthogonal linear drive systems; anX-direction drive 540, a Y-direction drive 542, a Z-direction drive 544,a fourth drive system 546 for swinging the flux regulator 550 in theplane of a predefined axis through angle Θ (less than 180 degree) (FIG.6A), and a fifth drive system 548 for rotating the flux regulator aboutits longitudinal axis through angle φ (less than 180 degree) (FIG. 6A).The flux regulator controller 540 is controlled by the control system570 to move (via rotary/linear motors) the flux regulator 550 to apredetermined position during ion beam sputter deposition of a targetmaterial on the workpiece 131. In the preferred embodiment of thepresent invention, the position of the movable flux regulator 550 in theX-direction, Y-direction and Z-direction is adjusted for each targetmaterial to be sputter deposited on the workpiece 131. A movable shutter510 is also located between the flux regulator 550 and the workpiece 531to block the incidence of atoms ejected from the target so that atomsreach the workpiece 531 only during the deposition steps.

Referring to FIGS. 6A and 7A-B, it should be noted that in thisembodiment when the substrate stage 541 is moved upward or downward, thedistance between the substrate stage 541 and the flux regulator 550remains constant since the flux regulator arm 553 is securely connectedto the stage arm 543. However, referring to FIG. 6B, in contrast, whenthe substrate stage 541 is moved upward or downward, the distancebetween the substrate stage 541 and the flux regulator 550 decreases orincreases, respectively since the movement of the stage arm 543 isindependent of the movement of the flux regulator shaft 551. Tilting thesubstrate stage 541 during the sputtering deposition process causes theatoms of the selected target material to hit the workpiece 531 at anon-normal angle thus improving the thickness uniformity as well aselectrical, physical and magnetic properties of the contiguous junctionformed between the materials deposited adjacent to each other on theworkpiece 531.

Now, referring to FIGS. 9A-9F, there is shown several steps inmanufacturing a plurality of SV sensors 900 on a workpiece (substrate)931 (similar to the wafer 300 shown in FIG. 3 and the wafer 531 shown inFIG. 5) using ion beam sputtering system 500 of the present inventionhaving the tiltable and rotatable substrate stage 541. In the preferredembodiment of the present invention as described below, workpiece 931 isrotating during all sputter deposition steps.

FIG. 9A is an ABS illustration showing a step after photoresists 995(photoresist1) and 990 (photoresist2) have been sequentially depositedover SV materials which is used to build a plurality of SV sensors 900.Although, many SV sensors 900 are built simultaneously on the substrate931 in the ion beam system of the present invention, the remainingdescription is limited to only one such SV sensor. As can be seen, freelayer 910 (typically made of NiFe or NiFe/Co), is first deposited overthe entire utilized area of the substrate 931 followed by sequentialdeposition of a non-magnetic spacer layer 915 (typically made of Cu, Agor Au), a pinned layer 920 (typically made of ferromagnetic (FM)material such as NiFe) which further includes a sub-layer 918 (typicallymade of Co), and an antiferromagnetic (AFM) layer 925 (typically made ofNio, FeMn or NiMn). Each layer is deposited with shape regulator 550 ata predetermined x position while the position of the shape regulator iny and z directions are fixed. The reference point for the purpose ofpositioning the shape regulator 550 is the center 539 (x=y=z=0) of thesubstrate stage 541. Table I shows uniformity data for several ion beamsputtered materials of the SV sensors 900 on a five inch diameter waferusing: (1) ion beam system of FIG. 1 having a non-movable flux regulator(fixed X-axis, Y-axis, and Z-axis positions for all the depositionsteps); and (2) the ion beam sputtering system of the present inventionhaving a movable flux regulator where the position of the movable fluxregulator in Y and Z directions were fixed and its X-axis position wasoptimized for each individual layer deposited. The improved uniformity,especially of the critical Cu spacer layer 915, achieved over the entireutilized area of the wafer results in manufacturing SV sensors that haveremarkably similar properties.

                  TABLE I                                                         ______________________________________                                        Uniformity of Deposited Layers                                                           Material  X-Setting (mm)                                                                           Uniformity (%)                                ______________________________________                                        Non-Movable                                                                              NiFe      +1.0       3.5                                             Flux Regulator Co +1.0 2.7                                                     Cu +1.0 11.3                                                                 Movable Flux NiFe +1.5 1.2                                                    Regulator Co +1.0 2.7                                                          Cu -1.0 3.7                                                                ______________________________________                                    

FIG. 9B is an ABS illustration showing a step in the manufacturing ofthe SV sensor 900 using the ion beam system 500 of the present inventionafter the development of the photoresist 990 and ion-milling of the SVmaterials. Note that ion-milling of the deposited SV materials resultsin sloped side edges 970 and 972.

FIG. 9C is an ABS illustration showing a step in the manufacturing ofthe SV sensor 900 using the ion beam system of the present inventionafter the deposition of the seed layers 980 and 985 in the end regions904 and 906, respectively, as well seed layer material deposition overphotoresist 990. In the preferred embodiment of the present invention,seed layers 980 and 985 are deposited by tilting the substrate stage 541(and therefore tilting the substrate 931) by a predetermined amount asshown in either FIG. 8B or FIG. 8C.

The aforementioned tilting step, as shown in FIG. 8B or FIG. 8C, resultsin sputtered atom flux 926_(a) or 926_(b) hitting the workpiece 931 atnon-normal angles resulting in the formation of the seed layers 980 and985 on the side edges 970 and 972, as well as on the exposed portions960 and 965 of the top surface of the substrate 931. The seed layersformed on the side edges 970 and 972 and the exposed portion 960 and 965of the substrate 931 are substantially uniform in their thicknesses dueto the fact that the substrate stage 541 was tilted and rotating duringthe deposition of the seed layer material. It should be noted that whenthe substrate stage 541 is tilted, the substrate 931 is also tiltedsince it is securely connected to the substrate stage 541 via, forexample, clamps or vacuum suction.

Note that seed layers 980 and 985 may be deposited in a single stepwhere the substrate stage 541 is either moved upward or downward (FIGS.7A-B), where the substrate stage 541 is tilted about its longitudinalaxis 537 (FIG. 6A) as shown in FIGS. 8A-8C, or where the substrate stage541 is moved upward or downward and at the same time tilted by apredetermined angle about its longitudinal axis. In the preferredembodiment of the present invention substrate stage 541 motions (movingup or down, tilting about its longitudinal axis, and the combination ofthe aforementioned motions is controlled by moving the stage arm 543about the connection point 568 using necessary mechanical gears as iswell known in the art.

FIG. 9D is an ABS illustration showing a step in the manufacturing ofthe SV sensor 900 using the ion beam system 500 of the present inventionafter the deposition of layers 930 and 935 of hard bias (HB) materialover the seed layers 980 and 985 in the end regions 904 and 906,respectively, as well as hard bias material deposition over photoresist990. Hard bias layers 930 and 935 are first partially deposited bysputtering hard bias atoms (sputtered atom flux 926_(a)) at a normalangle on the workpiece. Next, the substrate stage 541 is tilted in afirst direction by a predetermined angle (FIGS. 8A or 8B) and additionalhard bias material (sputtered atom flux 926_(b)) is deposited at the endregions 904 and 906 followed by tilting the substrate stage 541 in asecond direction by a predetermined angle (FIGS. 8A or 8B) fordepositing additional hard bias material (sputtered atom flux 926_(c))at the end regions 904 and 906. As a result of tilting the substratestage 541 during the bias material deposition step, the resulting hardbias layers 930 and 935 are uniformly thick and do not have a notch nearthe side edges 970 and 972. Alternatively, the step of depositing hardbias material in the end regions 904 and 906 may be carried out in asingle step of tilting the substrate stage 541 in a predetermineddirection by a predetermined angle and then sputter depositing hard biasmaterial in the end regions 904 and 906.

FIG. 9E is an ABS illustration showing a step in the manufacturing ofthe SV sensor 900 using the ion beam system 500 of the present inventionafter the deposition of lead layers 940 and 945 in the end regions 904and 906, respectively, as well as lead layer material deposition overthe photoresist 990. Lead layers 940 and 945 may be deposited in severalsteps by tilting the substrate stage 541 several times, each time at adifferent angle. As shown in FIG. 9E, lead layers 940 and 945 aredeposited through five partial depositions of sputtered atoms in the endregions 904 and 906. The partial depositions are carried out by firstdepositing sputtered atoms at normal angle (926_(a)), followed bydepositing atoms at a first non-normal angle (926_(b)) followed bydepositing atoms at a second non-normal angle (926_(c)), followed bydepositing sputtered atoms at a third non-normal angle (926_(d)),followed by depositing sputtered atoms at a fourth non-normal angle(926_(e)). Non-normal angles 926_(a), 926_(b), 926_(c) and 926_(d) aredue to sequentially tilting the stage substrate 541 in four differentpredetermined directions by predetermined angles. The aforementionedsteps result in lead layers 940 and 945 which are uniformly thick, donot have a notch near the side edges 970 and 972, make contacts to theAFM layer 925 and can partially fill the space created by undercuts 991and 992 in the photoresist 995. Alternatively, the step of depositinglead layer material in the end regions 904 and 906 may be carried out ina single step of tilting the substrate stage 541 in a predetermineddirection by a predetermined angle and then sputter depositing leadlayer material in the end regions 904 and 906.

FIG. 9F is an ABS view of a complete SV sensor 900 manufactured usingthe ion beam system of the present invention after photoresist 990 and995 have been removed. Comparing SV sensor 900 manufactured withApplicant's ion beam system 500 having a tiltable and rotatablesubstrate stage 541 with the SV sensor 200 manufactured with the ionbeam system 120 having a non-tiltable substrate stage, it can readily beseen that all the disadvantages and shortcomings of the SV sensor 200 isvirtually absent from SV sensor 900. That is, ion beam system 500 havinga tiltable substrate stage provides the necessary tool:

(i) to improve the uniformity of the material deposited adjacent to thematerials already deposited;

(ii) to improve the electrical and magnetic properties of the contiguousjunction formed between the materials deposited adjacent to each other;and

(iii) to eliminate any notching in the biasing layer which inducesdiscontinuity between hard bias material and the sensor materialresulting in MR sensor instability.

Referring now to FIG. 10, there is shown an schematic for an alternativeion beam system 500 of the present invention having a stage subsystem580. Stage subsystem 580 comprises a substrate stage 541 connected to astage shaft 566 which is in turn connected to a stage controller 560.Stage controller 560 in turn is connected to the control system 570 (notshown). In this embodiment, shaft 566 may tilt in X-direction,Y-direction or in XY-plane by pivoting about the pivot point 568 (vialinear motors) thus causing the tilting of the substrate stage 541.Alternatively, substrate stage 541 may tilt in X-direction, Y-directionor in XY-plane without tilting the stage shaft 566 via mechanical gearspositioned inside the stage shaft 566 which are capable of tilting thesubstrate stage 541. During sputter deposition process, substrate stage541 is made to rotate via rotating the stage shaft 566 via a rotarymotor (not shown). Use of mechanical gears, rotary and linear motors forcausing rotational and linear motions are well known in the art.

Referring now to FIG. 11, the effects of X-axis position of the movableflux regulator 550 are shown in graphs of the normalized sheetresistance as a function of location on the workpiece 931 (similar tothe substrate 300 shown in FIG. 3 and workpiece 531 shown in FIG. 5) forCu thin film depositions. It can readily be seen that the Cu filmuniformity which is used to form spacer 915, improves significantly from11.3% to 3.7% as the position of the movable flux regulator is changedfrom +1.0 mm to -1.0 mm in X direction while holding the position of themovable flux regulator in Y and Z directions the same.

Referring now to FIG. 12, the effects of X-axis position of the movableflux regulator 550 are shown in graphs of the normalized sheetresistance as a function of location on the workpiece for Co thin filmdepositions. It can readily be seen that the Co film uniformity which isused to form pinned layer 918, improves significantly from 9.0% to 2.7%as the position of the movable flux regulator is changed from +2.0 mm to+1.0 mm in X direction while holding the position of the movable fluxregulator in Y and Z directions the same.

Referring back to FIGS. 11 and 12, it can be seen that the X-axisposition of the movable flux regulator resulting in improved uniformityof the Cu film is different from the X-axis position of the movable fluxregulator resulting in improved uniformity of the Co film.

Note that in order to fabricate an SV sensor, multiple targets 523should include separate target for each material to be deposited. Forthe SV sensor 900 described above and illustrated in FIGS. 9A-9F,deposition of the structure in the central region 902 requires targetsfor the AFM pinning layer (NiO or NiMn or FeMn), the permalloy (NiFe)for pinned MR layer and free MR layer, the Co interface layer, thespacer layer (Cu or gold or silver) and the Ru layer if the pinned layeris an AP-pinned (FM/Ru/FM) layer. The free MR layer material isdeposited using the same target as for the ferromagnetic layers of thepinned MR layer. Furthermore, deposition of the structure in the endregions 904 and 906 requires targets for the seed layer of Cr, for thehard bias layer of CoPtCr and for the lead layer of Ta. For each targetmaterial, in order to achieve the optimum X-axis setting of the movableflux regulator, an experiment is carried out where a set of thin filmsare sputter deposited on substrates using a different X-axis setting forthe movable flux regulator 550 for each film. The film thicknessuniformity of each film is measured across the substrate diameter usingan appropriate measure such as, for example, sheet resistance. Thegraphs of FIG. 11 and 12 show results obtained for Cu films and Cofilms, respectively. As a result of carrying out the aforementionedexperiments, a setting for the X-axis position of the movable fluxregulator is chosen which achieves the highest thickness uniformity foreach layer of material to be deposited on a wafer substrate. The chosensettings for the movable flux regulator are the settings that will beused during subsequent depositions of the multilayers of the MR sensors.

While the present invention has been particularly shown and describedwith reference to the preferred embodiment thereof, nevertheless, itwill be understood by those skilled in the art that variousmodifications may be made therein without departing from the spirit,scope, and teaching of the present invention.

For example, although the ion beam system of the present invention wasmainly utilized to improve the physical, electrical and magneticproperties as well as thickness uniformity of the layers deposited on awafer substrate for making MR sensors, the invention is equallyapplicable to any art that may benefit from improved electrical,physical and magnetic properties and thickness uniformity of an ion beamsputter deposited layer on a substrate.

Furthermore, while a circular substrate stage 541 was utilized in thepreferred embodiment of the present invention, an elliptical, square,rectangular, triangular, diamond or any other shape may be used withoutdeparting from the spirit of this invention.

Furthermore, although a tilting stage shaft or a rotating and tiltingstage arm was used to tilt the substrate stage 541, other schemes may beemployed to cause the tilting of the substrate stage without departingfrom the spirit of this invention.

Accordingly, it is to be understood that the invention disclosed hereinis not to be limited by the illustrated embodiment, but only by thescope of the appended claims.

I claim:
 1. An ion-beam sputtering deposition system comprising:a vacuumchamber; a target of material in said vacuum chamber; an ion-beam sourcefor directing ions at said target for depositing said target material ona wafer placed in said vacuum chamber; a substrate stage for holdingsaid wafer, said substrate stage being capable of tilting in a firstdirection and in a second direction before or during the deposition ofsaid target material; and a movable flux regulator, disposed betweensaid target and said wafer, for partially blocking a portion of saidtarget material from being deposited on said wafer during the depositionof said target material, wherein said movable flux regulator is movablein X-axis, Y-axis and Z-axis directions relative to said wafer.
 2. Anion-beam sputtering deposition system comprising:a vacuum chamber; atarget of material in said vacuum chamber; an ion-beam source fordirecting ions at said target for depositing said target material on awafer placed in said vacuum chamber; a movable flux regulator positionedbetween said target and said wafer for partially blocking a portion ofsaid target material from depositing on said wafer during deposition ofsaid target material, wherein said movable flux regulator is movable inX-axis, Y-axis and Z-axis directions relative to said wafer; a shutterpositioned between said movable flux regulator and said wafer; and atiltable substrate stage for holding said wafer during the deposition ofsaid target material, said substrate stage being capable of tilting in afirst direction and in a second direction before or during thedeposition of said target material.
 3. The ion-beam sputteringdeposition system according to claim 2, wherein said tiltable substratestage can further rotate about its vertical axis during the depositionof said target material.
 4. An ion-beam sputtering deposition systemcomprising:a vacuum chamber; a target of material in said vacuumchamber; an ion-beam source for directing ions at said target fordepositing said target material on a wafer; a movable flux regulatorpositioned between said target and said wafer for partially blocking aportion of said target material from depositing on said wafer duringdeposition of said target material, wherein said movable flux regulatoris movable in X-axis, Y-axis and Z-axis directions relative to saidwafer; a shutter positioned between said movable flux regulator and saidwafer; and a tiltable substrate stage for holding said wafer during thedeposition process, said substrate stage being capable of tilting in afirst direction and in a second direction before or during thedeposition of said target material, said tiltable substrate stage havinga vertical axis, said tiltable substrate stage forming a non-normalangle with respect to said vertical axis during the deposition of saidtarget material.
 5. The ion-beam sputtering deposition system accordingto claim 4, wherein said tiltable substrate stage further rotates aboutsaid vertical axis during the deposition of said target material.
 6. Anion-beam sputtering deposition system comprising:a vacuum chamber; aplurality of targets of materials in said vacuum chamber; an ion-beamsource for directing ions at said plurality of targets for sequentiallydepositing a number of said target materials on a wafer; a movable fluxregulator positioned between said plurality of targets and said waferduring deposition of said target material for controlling the thicknessuniformity of each of said number of target materials deposited on saidwafer, wherein said movable flux regulator is movable in X-axis, Y-axisand Z-axis directions relative to said substrate; and a tiltablesubstrate stage, said substrate stage being capable of tilting in afirst direction and in a second direction before or during thedeposition of said target material, said wafer being placed on saidtiltable substrate stage during the deposition of said number of targetmaterials, said wafer having a vertical axis, said wafer forming anon-normal angle with respect to said vertical axis during thedeposition of said number of target materials on said wafer.
 7. Theion-beam sputtering deposition system according to claim 6, wherein saidtiltable substrate can further rotate during the deposition of saidnumber of target materials on said wafer.
 8. The ion-beam sputteringdeposition system according to claim 6, wherein said non-normal angle isadjusted based on the target material being deposited on said wafer. 9.The ion-beam sputtering deposition system according to claim 6 furthercomprising a rotatable stage for rotating said plurality of targetmaterials.
 10. The ion-beam sputtering deposition system according toclaim 6 wherein one of said plurality of target materials is copper. 11.The ion-beam sputtering deposition system according to claim 6 whereinone of said plurality of target materials is cobalt.
 12. The ion-beamsputtering deposition system according to claim 6 wherein one of saidplurality of target materials is Ni--Fe.
 13. The ion-beam sputteringdeposition system according to claim 6 wherein one of said plurality oftarget materials is NiMn.
 14. The ion-beam sputtering deposition systemaccording to claim 6 wherein one of said plurality of target materialsis NiO.
 15. The ion-beam sputtering deposition system according to claim6 wherein one of said plurality of target materials is Ni.
 16. Theion-beam sputtering deposition system according to claim 6 wherein oneof said plurality of target materials is Ru.
 17. The ion-beam sputteringdeposition system according to claim 6 wherein one of said plurality oftarget materials is Ta.
 18. The ion-beam sputtering deposition systemaccording to claim 6 wherein one of said plurality of target materialsis Cr.
 19. The ion-beam sputtering deposition system according to claim6 wherein one of said plurality of target materials is CoPtCr.
 20. Amethod of building a magnetoresistive sensor on a wafer in an ion-beamsputtering system having a vacuum chamber, a plurality of targetmaterials in said vacuum chamber, an ion-beam source, a movable fluxregulator and a tiltable substrate stage for holding said wafer, saidsubstrate stage being capable of tilting in a first direction and in asecond direction before or during the deposition of said targetmaterial, said method comprising the steps of:depositing an MR materialon said wafer, said MR material including two layers of ferromagneticmaterial separated from each other by a layer of non-magnetic material;depositing photoresist material on said MR material followed bypatterning and developing said photoresist to create openings in saidphotoresist material; removing said MR material exposed through saidopenings; sputter depositing atoms of a first target material on saidwafer substrate while said wafer substrate is tilted to form a firstnon-normal angle with respect to its vertical axis; and sputterdepositing atoms of a second target material on said first targetmaterial while said wafer substrate is tilted to form a secondnon-normal angle with respect to its vertical axis.
 21. The methodaccording to claim 20 wherein said first target material is Cr.
 22. Themethod according to claim 20 wherein said second target material isCoPtCr.
 23. The method according to claim 20 further including a step ofsputter depositing atoms of a third target material on said secondtarget material while said wafer substrate is tilted to form a thirdnon-normal angle with respect to its vertical axis.
 24. The methodaccording to claim 23 wherein said third target material is Ta.
 25. Anion-beam sputtering deposition system comprising:a vacuum chamber; asubstrate stage for holding a wafer substrate, said substrate stagebeing capable of tilting in a first direction and in a second directionbefore or during the deposition of said target material to form anon-normal angle with its vertical axis; a target of material; anion-beam source for directing ions at said target for depositing saidmaterial on said wafer substrate; and a movable flux regulator, disposedbetween said target and said wafer substrate during the deposition ofsaid target material, for controlling the uniformity of the targetmaterial deposited on said wafer substrate, wherein said movable fluxregulator is movable in X-axis, Y-axis and Z-axis directions relative tosaid substrate.